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PubMed1986

Pulse oximetry and circulatory kinetics associated with pulse volume amplitude measured by photoelectric plethysmography.

Through a catheter placed in a superficial vein on the finger, we observed a pulsatile venous pressure. To delineate the relationship between the pulsatile venous pressure and the pulse volume amplitude (PVA) recorded by photoelectric plethysmography (PEPG), both tracings were simultaneously recorded. When the PVA changed acutely or gradually, the venous pulse pressure and mean venous pressure simultaneously followed the same trend. We also found that mean PVO2 (135 mm Hg) was greater when the PVA and venous pulse pressure increased above the level (50 mm Hg) observed when they decreased. These findings suggested that the finger pulse detected by PEPG, as well as by pulse oximetry, is caused by pulsations in veins rather than by pulsations in arterial beds. In experiments to evaluate the validity of this hypothesis, we found that the average value of hemoglobin saturation (%SaO2) measured by the pulse oximeter of the dependent fingertip and finger base when dependent was 1.5% and 7.8% lower than when the fingertip and finger base were elevated. Also, the PVA detected by the pulse oximeter followed the same trend as %SaO2. This finding was explained by venous congestion in the dependent finger. On the basis of the high venous pressure, the behavioral trends between the PVA and venous pressure, the high PVO2, and the low %SaO2 and PVA in the dependent finger, we conclude that the PVA of the PEPG is determined mainly by venous pulse volume generated by shunting of arterial pulse via open arteriovenous (AV) anastomoses in the cutaneous circulation.

Adult↗
PubMed1971

The effects of altering mean pressure, pulse pressure and pulse frequency on the impulse activity in baroreceptor fibres from the aortic arch and right subclavian artery in the rabbit.

1. A method is described for perfusing an isolated preparation of the rabbit aortic arch with independently controlled mean pressure, pulse pressure and pulse frequency.2. Recordings made from single or few-fibre preparations from the aortic arch and right subclavian baroreceptor regions show that the number of impulses per second or per cycle in a single fibre is the same during pulsatile perfusion as during non-pulsatile perfusion if the pressure is above the threshold pressure to non-pulsatile perfusion during all phases of the pressure cycle.3. In multi-fibre recordings the total number of impulses is greater during pulsatile perfusion than during non-pulsatile perfusion due largely to recruitment of fibres during systole.4. The relationship between instantaneous impulse frequency and aortic arch pressure during one pressure cycle forms an elliptiform curve.5. Increasing the pulse pressure increases the ellipse and causes additional recruitment of other fibres during systole, thus augmenting the total impulse activity.6. Increasing the pulse frequency reduces the number of impulses per cycle for single fibres but produces a small increase in the total impulse frequency in one second period due to recruitment.7. Increasing the rate of change of pressure by increasing the pulse pressure or pulse frequency produced a small reduction or no change of the threshold pressure. Similarly the ;cut off' pressure was elevated in some fibres.8. At low initial mean pressures, an increment of pressure, at constant pulse pressure and pulse frequency, increases the total impulse activity by increasing the frequency of impulses in single fibres already active during systole and diastole and by additional recruitment of other fibres. At higher mean pressures there is little increase in impulse activity as the maximum frequency of fibres is attained or superseded and there is little recruitment.

Action Potentials↗
PubMed2001

Telomere length as an indicator of biological aging: the gender effect and relation with pulse pressure and pulse wave velocity.

Chronological age is the primary determinant of stiffness of central arteries. Increased stiffness is an independent indicator of cardiovascular risk. The aim of this study was to determine whether telomere length, a possible index of biological aging, provides a better account than chronological age for variation in arterial stiffness, evaluated by measuring pulse pressure and aortic pulse wave velocity. The study population included 193 French subjects (120 men, 73 women), with a mean age of 56+/-11 years, who were not on any antihypertensive medications. Telomere length was evaluated in white blood cells by measuring the mean length of the terminal restriction fragments. Age-adjusted telomere length was longer in women than in men (8.67+/-0.09 versus 8.37+/-0.07 kb; P=0.016). In both genders, telomere length was inversely correlated with age (P<0.01). Multivariate analysis showed that in men, but not in women, telomere length significantly contributed to pulse pressure and pulse wave velocity variations. In conclusion, telomere length provides an additional account to chronological age of variations in both pulse pressure and pulse wave velocity among men, such that men with shorter telomere length are more likely to exhibit high pulse pressure and pulse wave velocity, which are indices of large artery stiffness. The longer telomere length in women suggests that for a given chronological age, biological aging of men is more advanced than that of women.

Age Factors↗
PubMed1999

Long-pulsed alexandrite laser-assisted hair removal at 5, 10, and 20 millisecond pulse durations.

BACKGROUND: Several laser systems with varying wavelengths, pulse durations, and energy fluences are currently utilized for hair removal. However, the ideal laser parameters and treatment candidates for photoepilation remain largely unknown. The medical literature lacks a wealth of experimental data to sufficiently document the long-term safety and efficacy of laser-assisted hair removal. This study examines the clinical efficacy and side effect profile of long-pulsed alexandrite laser-assisted hair removal utilizing laser pulse durations of either 5, 10, or 20 milliseconds (ms). STUDY DESIGN/METHODS: Laser-assisted hair removal was performed on 36 subjects with a long-pulsed alexandrite laser. Areas of unwanted hair growth on the face, back, and legs were divided linearly into four 1 cm2 or 2 cm2 quadrants. Experimental regions included a control quadrant and three additional quadrants, which were treated with the alexandrite laser using an average fluence of 18 J/cm2, with a 10 mm spot size at either a 5, 10, or 20 ms pulse duration. Hair counts and photographs were obtained before treatment, immediately following irradiation, 1 week and 1, 3, and 6 months postoperatively. RESULTS: All laser-treated quadrants displayed a significant delay in hair regrowth compared to control nontreated quadrants at postoperative week 1 and months 1 and 3. Hair counts were reduced by 66% at 1 month, 27% at 3 months, and 4% at 6 months. No significant differences in clinical efficacy or side effect profiles were observed between treatment quadrants, yet a trend towards less post-treatment erythema and hyperpigmentation was noted with the 20 ms pulse duration. CONCLUSIONS: Equivalent long-term hair removal for up to 6 months was achieved with the long-pulsed alexandrite laser at 5, 10, and 20 ms pulse durations at an average fluence of 18 J/cm2. Side effects were limited and transient.

Adult↗
PubMed1984

Luteinizing hormone releasing hormone of fixed pulse frequency and duration. A simplified system for studying the effect of varying pulse concentration on LH release from cytodex I attached anterior pituitary cells.

The literature indicates agreement concerning basic differences in the behavior of the pituitary toward pulsatile and continuous luteinizing hormone releasing hormone (LHRH); however, conflicting results seem to exist concerning pituitary behavior toward pulsatile LHRH (Hopkins, 1977; Smith and Vale, 1981). Most superfusion studies have utilized pulses of 15-30 minutes during which the cells were exposed to pharmacological quantities of LHRH. Differences in results may have arisen because of the varying methodologies utilized to administer pulse frequency, pulse duration, and pulse concentration; therefore, the present studies utilized standardized methodology in which the LHRH pulse frequency and pulse duration were maintained constant while the pulse concentration was varied. Pulsatile LHRH of fixed concentration was associated with a relatively rapid loss of responsiveness, while small increases in each subsequent pulse served to prolong the period of responsiveness. The results indicated that seemingly small changes in the methological pattern of LHRH stimulation are capable of exerting an influence on the response to subsequent LHRH stimulation. Caution should therefore be exerted in comparing the results from different experiments utilizing different methodological designs for applying LHRH stimulation. In practical terms, these studies indicate that results must be interpreted carefully from experiments in which a fixed pool of pituitary cells has been repeatedly stimulated by LHRH. This is especially true with dose-response curves generated by this method and with experiments designed to study LHRH self-priming and desensitization.

Animals↗
PubMed1991

The consistency of pulse frequencies and pulse patterns of transcutaneous electrical nerve stimulation (TENS) used by chronic pain patients.

This study records the consistency of transcutaneous electrical nerve stimulation (TENS) pulse frequency and pulse pattern used by 13 chronic patients over a 1 year period. The results show that patients prefer specific pulse frequencies and pulse patterns unique to the individual and that they turn to such frequencies and patterns on subsequent treatment sessions. Pulse frequencies and pulse patterns were not related to the cause and site of pain, a finding consistent with previous study in this laboratory. This observation, coupled with the large variability in pulse frequencies and pulse patterns used between individuals, implies that patients prefer such frequencies and patterns for reasons of comfort which may not be related to mechanisms specific to the pain system.

Adult↗
PubMed2001

Comparison of long-pulsed diode and long-pulsed alexandrite lasers for hair removal: a long-term clinical and histologic study.

BACKGROUND: Unwanted facial and body hair is a common problem, generating a high level of interest for treatment innovations. Advances in laser technology over the past several years has led to the development and distribution of numerous red and infrared lasers and light sources to address this issue. Despite the impressive clinical results that have been reported with the use of individual laser hair removal systems, long-term comparative studies have been scarce. OBJECTIVE: To compare the clinical and histologic efficacy, side effect profile, and long-term hair reduction of long-pulsed diode and long-pulsed alexandrite laser systems. METHODS: Twenty women with Fitzpatrick skin types I-IV and dark terminal hair underwent three monthly laser-assisted hair removal sessions with a long-pulsed alexandrite laser (755 nm, 2-msec pulse, 10 mm spot) and a long-pulsed diode laser (800 nm, 12.5 msec or 25 msec, 9 mm spot). Axillary areas were randomly assigned to receive treatment using each laser system at either 25 J/cm2 or 40 J/cm2. Follow-up manual hair counts and photographs of each area were obtained at each of the three treatment visits and at 1, 3, and 6 months after the final laser session. Histologic specimens were obtained at baseline, immediately after the initial laser treatment, and 1 and 6 months after the third treatment session. RESULTS: After each laser treatment, hair counts were successively reduced and few patients found it necessary to shave the sparsely regrown hair. Optimal clinical response was achieved 1 month after the second laser treatment, regardless of the laser system or fluence used. Six months after the third and final treatment, prolonged clinical hair reduction was observed with no significant differences between the laser systems and fluences used. Histologic tissue changes supported the clinical responses observed with evidence of initial follicular injury followed by slow follicular regeneration. Side effects, including treatment pain and vesiculation, were rare after treatment with either laser system, but were observed more frequently with the long-pulsed diode system at the higher fluence of 40 J/cm2. CONCLUSION: Equivalent clinical and histologic responses were observed using a long-pulsed alexandrite and a long-pulsed diode laser for hair removal with minimal adverse sequelae. While long-term hair reduction can be obtained in most patients after a series of laser treatments, partial hair regrowth is typical within 6 months, suggesting the need for additional treatments to improve the rate of permanent hair removal.

Adult↗
PubMed2004

Resurfacing of different types of facial acne scar with short-pulsed, variable-pulsed, and dual-mode Er:YAG laser.

BACKGROUND: Laser skin resurfacing has become a popular therapeutic modality for the correction of acne scars, but it is not always effective in all types of acne scars. OBJECTIVE: To evaluate the clinical effects of resurfacing with the short-pulsed Er:YAG laser, the variable-pulsed Er:YAG laser, and the dual-mode Er:YAG laser for each type of facial acne scars. METHODS: One hundred fifty-eight patients with facial acne scars were included in this study. Eighty three patients (18 deep boxcar scars, 8 ice-pick scars, 11 rolling scars, and 46 shallow boxcars) were treated with the 350-micros short-pulsed Er:YAG laser at the setting of 12.5 to 15%/cm(2). Thirty-five patients (8 deep boxcar scars, 4 ice-pick scars, 12 rolling scars, and 11 shallow boxcars) were treated with the variable-pulsed Er:YAG laser at the setting of 7.0 to 7.5%/cm(2) and 7-ms pulse duration. Forty patients (8 deep boxcar scars, 4 ice-pick scars, 17 rolling scars, and 11 shallow boxcars) were treated with the dual-mode Er:YAG laser with 350-micro ablation mode at 17.5%/cm(2) and 8-ms coagulation mode at 3.15%/cm(2). Facial photographs were obtained at baseline and at 2- to 4-week intervals postoperatively. Acne scars were classified into four types, and clinical improvements of facial acne scars were evaluated. RESULTS: Resurfacing with the short-pulsed Er:YAG laser shows good to excellent results for ice-pick and shallow boxcar scars, fair to good for deep boxcar scars, and poor to fair for rolling scars. Resurfacing with the variable-pulsed laser shows good to excellent results for ice-pick and shallow boxcar scars, fair to good for deep boxcar scars, and good for rolling scars. Resurfacing with the dual-mode laser shows good to excellent results for ice-pick, shallow, and rolling scars and produced good results on deep boxcar scars. CONCLUSION: Shallow boxcar and ice-pick scars can be treated successfully using any types of Er:YAG laser. In cases of rolling and deep boxcar scars, however, Er:YAG laser with a long-pulse duration for a thermal effect is needed for successful treatment.

Acne Vulgaris↗
PubMedDate not supplied

Visible lesion thresholds with pulse duration, spot size dependency, and model predictions for 1.54-microm, near-infrared laser pulses penetrating porcine skin.

Er:glass lasers have been in operation with both long pulses (hundreds of microseconds) and Q-switched pulses (50 to 100 ns) for more than 35 yr. The ocular hazards of this laser were reported early, and it was determined that damage to the eye from the 1.54-microm wavelength occurred mainly in the cornea where light from this wavelength is highly absorbed. Research on skin hazards has been reported only in the past few years because of limited pulse energies from these lasers. Currently, however, with pulse energies in the hundreds of joules, these lasers may be hazardous to the skin in addition to being eye hazards. We report our minimum visible lesion (MVL) threshold measurements for two different pulse durations and three different spot sizes for the 1.54-microm wavelength using porcine skin as an in vivo model. We also compare our measurements to results from our model, based on the heat transfer equation and the rate process equation. Our MVL-ED50 thresholds for the long pulse (600 micros) at 24 h postexposure were measured to be 20, 8.1, and 7.4 J cm(-2) for spot diameters of 0.7, 1.0, and 5 mm, respectively. Q-switched laser pulses of 31 ns had lower ED50 (estimated dose for a 50% probability of laser-induced damage) thresholds of 6.1 J cm(-2) for a 5-mm-diam, top-hat spatial profile laser pulse.

Animals↗
PubMed1993

Graded hyperprolactinemia first suppresses LH pulse frequency and then pulse amplitude in castrated male rats.

We recently demonstrated that the ability of administered ovine prolactin (oPRL) to suppress postcastration LH secretion exhibited a clear dose dependency. In the present study, we determined whether this dose-related suppression of mean LH levels resulted from differential, dose-related effects of oPRL on LH pulse amplitude and pulse frequency. Adult male rats were orchiectomized and adrenalectomized, implanted with an atrial cannula and a 50% corticosterone pellet, and injected every 12 h with oPRL or its polyvinylpyrrolidone (PVP) vehicle beginning at time 0. Increasing doses of oPRL (600, 2,400 and 9,600 micrograms/injection) suppressed mean LH titers in a dose-dependent manner at 48 h postcastration. The mean maximal LH increments (delta LH) to two LHRH challenges at two doses (5 and 25 ng LHRH/100 g body weight) were unaffected by oPRL administration. The 600 micrograms oPRL dose significantly suppressed mean LH values by markedly increasing the inter-peak interval (42.6 +/- 6.7 min) compared with controls (26.6 +/- 0.2 min) since the pulse amplitude was unaffected (2.8 +/- 0.4 vs. 2.6 +/- 0.4 ng/ml, respectively). The two higher oPRL doses suppressed both LH pulse frequency and pulse amplitude. Hence, elevated PRL levels first suppress LH pulse frequency and then, at higher concentrations, pulse amplitude as well. Presuming that LHRH pulses result from ensemble firing of all or a significant proportion of the LHRH neurons projecting to the median eminence, the present data suggest that the neurons first affected by elevated PRL levels are the ones responsible for this frequency of this coordinated firing.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed2005

Relation between respiratory variations in pulse oximetry plethysmographic waveform amplitude and arterial pulse pressure in ventilated patients.

INTRODUCTION: Respiratory variation in arterial pulse pressure is a reliable predictor of fluid responsiveness in mechanically ventilated patients with circulatory failure. The main limitation of this method is that it requires an invasive arterial catheter. Both arterial and pulse oximetry plethysmographic waveforms depend on stroke volume. We conducted a prospective study to evaluate the relationship between respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic (POP) waveform amplitude. METHOD: This prospective clinical investigation was conducted in 22 mechanically ventilated patients. Respiratory variation in arterial pulse pressure and respiratory variation in POP waveform amplitude were recorded simultaneously in a beat-to-beat evaluation, and were compared using a Spearman correlation test and a Bland-Altman analysis. RESULTS: There was a strong correlation (r2 = 0.83; P < 0.001) and a good agreement (bias = 0.8 +/- 3.5%) between respiratory variation in arterial pulse pressure and respiratory variation in POP waveform amplitude. A respiratory variation in POP waveform amplitude value above 15% allowed discrimination between patients with respiratory variation in arterial pulse pressure above 13% and those with variation of 13% or less (positive predictive value 100%). CONCLUSION: Respiratory variation in arterial pulse pressure above 13% can be accurately predicted by a respiratory variation in POP waveform amplitude above 15%. This index has potential applications in patients who are not instrumented with an intra-arterial catheter.

Adult↗
PubMed1985

Gonadotropin-releasing hormone pulses in third ventricular cerebrospinal fluid of ovariectomized rhesus monkeys: correlation with luteinizing hormone pulses.

Morphological evidence suggests that GnRH may be released into cerebrospinal fluid (CSF) of the third ventricle. Therefore, a method of cannulating the third ventricle of monkey brains was developed for the purpose of examining GnRH secretion in primates. A stainless steel guide cannula was stereotaxically implanted into the third ventricle of 14 ovariectomized rhesus monkeys. A Silastic cannula for collecting CSF was inserted via the guide cannula into the ventral portion of the ventricle, permitting repeated CSF sampling for long time periods from the same animal. One week to 6 months after cannulation, CSF was collected continuously for periods of 5-10 h at 2 different rates (480 and 120 microliter/h) from conscious monkeys seated in chairs. Samples were divided into 15-min fractions, and the GnRH concentration in each was determined by RIA. In contrast to most previous studies, third ventricular CSF was found to contain significant concentrations of GnRH. GnRH was detected in 40 of 50 collections. Concentrations ranged from less than 8 to greater than 800 pg/ml, a range similar to that observed in hypophyseal portal blood. Furthermore, fluctuations within individual collections indicated that GnRH was released in pulses. The mean GnRH pulse frequency during the higher rate of CSF withdrawal was 0.43 +/- 0.06 pulses/h (n = 31), while the mean pulse amplitude was 91 +/- 7 pg/ml (n = 64). Neither parameter was influenced by the rate of CSF removal, as frequency was 0.52 +/- 0.08 pulses/h (n = 19) and amplitude was 94 +/- 11 pg/ml (n = 82) during the lower collection rate. However, the CSF withdrawal rate had a profound influence on LH secretion. In 12 of 17 collections at the higher rate, LH levels plummeted to undetectable concentrations during the first 2 h of CSF exfusion and remained low throughout the collection period. Pituitary responsiveness was not reduced, as a GnRH bolus (0.25 or 2.5 micrograms) after 6 h of CSF removal elicited a dose-dependent stimulation of LH secretion. In contrast, a higher incidence of normal pulsatile LH secretion (12 of 19 collections) was observed when the CSF withdrawal rate was reduced. During these 12 collections, LH and GnRH pulses occurred at regular intervals and exhibited similar pulse frequencies (mean +/- SE, 0.76 +/- 0.07 and 0.67 +/- 0.09 pulses/h for LH and GnRH, respectively). Most GnRH and LH pulses were synchronized, as 86% of all GnRH pulses (43 of 50) were accompanied by a LH pulse.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

Pulsed radiofrequency of the dorsal root ganglia is superior to pharmacotherapy or pulsed radiofrequency of the intercostal nerves in the treatment of chronic postsurgical thoracic pain.

BACKGROUND: Chronic postsurgical thoracic pain (CPTP) represents a major therapeutic challenge characterized by an absence of clinical studies to guide treatment. Recently, the implementation of pulsed radiofrequency (RF) has generated intense interest in the medical community as a safe and potentially effective treatment for neuropathic pain. To date, there are no studies comparing pulsed RF to more conventional therapeutic modalities for any pain condition. OBJECTIVES: To compare treatment outcomes between pharmacotherapy, pulsed RF of the intercostal nerves (ICN) and pulsed RF of the dorsal root ganglia (DRG) in CPTP. METHODS: Retrospective data analysis involving 49 patients. RESULTS: At 6-week follow-up, 61.5% of the pulsed RF DRG group reported > or =50% pain relief vs. 27.3% in the medical management (MM) group and 21.4% in the IC group (P = 0.12). At 3-month follow-up, 53.8% in the DRG group continued to report > or = 50% pain relief vs. 19.9% in the MM and 6.7% in the ICN groups, respectively (P = 0.02). Among the pulsed RF patients who did report a successful outcome, the mean duration of pain relief was 2.87 months in the ICN group and 4.74 months in the DRG group (P = 0.01). CONCLUSIONS: Pulsed RF of the DRG was a superior treatment to pharmacotherapy and pulsed RF of the ICN in patients with CPTP. Prospective studies are needed to confirm these results and identify the best candidates for this treatment.

Adult↗
PubMed1989

Pulse, a PC-based graphics pulse sequence editor for NMR and MRI.

A flexible, personal computer (PC) based, screen-graphics oriented pulse sequence editor called PULSE has been developed for nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI). PULSE is used to set such NMR spectroscopic parameters as the delay and duration of rf transmit and receive gates, rf phase, sampling times, and such imaging parameters as rf pulse shape and gradient waveforms. The output of PULSE is a set of programs that can be loaded into a hardware pulse programmer. With PULSE, any desired NMR or MRI pulse sequence can be programmed quickly and easily.

Computer Graphics↗
PubMed2006

Endothelial function is associated with pulse pressure, pulse wave velocity, and augmentation index in healthy humans.

Arterial stiffness is an independent predictor of mortality and is regulated by a number of factors, including vascular smooth muscle tone. However, the relationship between endothelial function and definitive measures of arterial stiffness and wave reflections has not been described in healthy individuals. Therefore, we tested the hypothesis that endothelial function is inversely correlated with aortic pulse wave velocity (PWV), central pulse pressure, and augmentation index in healthy individuals. Peripheral and central pulse pressure and augmentation index were determined at rest, and global endothelial function was measured using pulse wave analysis and administration of sublingual nitroglycerin and inhaled albuterol. Aortic PWV was also determined at baseline in a subset of 89 subjects. In a separate group of subjects (n=89), aortic PWV was measured and brachial artery flow-mediated dilatation assessed as a measure of conduit artery endothelial function. Global endothelial function was significantly and inversely correlated with aortic PWV (r=-0.69; P<0.001), augmentation index (r=-0.59; P<0.001), and central (r=-0.34; P<0.001) and peripheral pulse pressure (r=-0.15; P=0.03). Moreover, there was a stronger correlation between central rather than peripheral pulse pressure. After adjusting for potential confounders, global endothelial function remained independently and inversely associated with aortic PWV and augmentation index. There was also a significant, inverse relationship between conduit artery endothelial function and aortic PWV (r=0.39, P<0.001), which remained independent after adjusting for confounding factors. In healthy individuals, a decline in endothelial function is associated with increased large artery stiffness, wave reflections, and central pulse pressure.

Administration, Inhalation↗
PubMed2005

Influence of pulsed electromagnetic field with different pulse duty cycles on neurite outgrowth in PC12 rat pheochromocytoma cells.

The influence of low frequency (50 Hz repetition rate) pulsed electromagnetic field (EMF) on PC12 cell neurite outgrowth in vitro was investigated in this study. We studied the percentage of neurite bearing cells, average length of neurites, and directivity of neurite outgrowth in PC12 cells cultured for 96 h in the presence of nerve growth factor (NGF). PC12 cells were exposed in one incubator to pulsed EMF at 1.36 mT (peak value) generated by a pair of Helmholtz coils, and the control samples were placed in another identical incubator. We found that the pulse duty cycle had significant effect on neurite outgrowth. Low (10%) pulse on-time significantly inhibited the percentage of neurite bearing cells, but at the same time increased the average length of neurites, while 100% on-time (DC) had exactly the opposite effects. Furthermore, we found that neurites were prone to extend along the direction of pulsed EMF with 10% pulse on-time. Our studies show that neurite outgrowth in PC12 cells is sensitive to the pulse duty and this sensitivity was associated with NGF concentration.

Animals↗
PubMed2001

Laser resurfacing with a long pulse erbium:YAG laser compared to the 950 ms pulsed CO(2) laser.

BACKGROUND AND OBJECTIVE: Laser resurfacing with the 950 micros pulsed CO(2) laser is an effective treatment for photodamage and acne scarring; however, the potential for prolonged erythema and delayed re-epithelialization dissuade many patients from the procedure. With the use of erbium lasers alone, there is a decrease in the incidence and severity of these adverse sequelae; however, it is difficult to achieve the same degree of improvement as with the CO(2) laser because of the more superficial depth of resurfacing. Thus, new erbium lasers have been developed with longer pulse durations to deliver increased thermal effects to tissue. It is hypothesized that with the use of these lasers, diminished erythema and faster wound healing will be observed as well as enhanced clinical outcomes. STUDY DESIGN/MATERIALS AND METHODS: Sixteen patients were randomized to receive laser resurfacing on one-half of the face with the 950 micros pulsed CO(2) laser (UPCO(2)) followed by short pulse erbium:YAG ablation, and to the other half with a variable pulsed erbium laser (VP Er:YAG) followed by traditional short pulse erbium laser. Patients were evaluated clinically before resurfacing and at 1, 2, 4, 8, and 12 weeks post-operatively. Histologic samples taken at various time periods before and after resurfacing were also evaluated. RESULTS: Overall clinical improvement was equal for both UPCO(2) and VP Er:YAG treated sides with an average improvement in photoaging scores of 57%. Decreased erythema, less edema, and faster healing were observed on the VP Er:YAG treated side. CONCLUSION: The VP Er:YAG laser can achieve a similar degree of improvement as seen with short pulse CO(2) laser resurfacing with decreased thermal tissue effects and decreased risk for adverse sequelae.

Face↗
PubMed2005

Efficacy of the 1.5 millisecond pulse-duration, 585 nm, pulsed-dye laser for treating port-wine stains.

BACKGROUND AND OBJECTIVES: Some reports have suggested that 1.5-millisecond pulse-duration pulsed-dye lasers (PDLs) may have increased efficacy in treating port-wine stains (PWSs) as compared to previous generation lasers. We study the efficacy of the 1.5-millisecond pulse-duration PDL for treating PWSs. STUDY DESIGN/MATERIALS AND METHODS: We treated 104 areas of involvement by PWSs in 95 subjects with the 1.5-millisecond pulse-duration PDL. Subjective and objective measures of improvement were utilized. Twenty-one of these PWSs had failed treatment with earlier generation PDLs. RESULTS: PWSs previously refractory to the shorter pulse duration lasers responded well to treatment, as did PWSs not previously treated with any laser. CONCLUSIONS: The 1.5-millisecond pulse-duration PDL is effective for treating PWSs and may offer improved efficacy over shorter pulse-duration lasers.

Adolescent↗